MathDB
Area in Geometry

Source: 2000 National High School Mathematics League, Exam Two, Problem 1

March 11, 2020
geometrycircumcircle

Problem Statement

In acute triangle ABCABC, D,ED,E are two points on side BCBC, satisfying that BAE=CAF\angle BAE=\angle CAF. FMAB,ENACFM\perp AB,EN\perp AC (M,NM,N are foot points). AEAE intersects the circumcircle of ABC\triangle ABC at DD. Prove that the area of ABC\triangle ABC and quadrilateral AMDNAMDN are equal.